Light-emitting device and method of fabricating the same

ABSTRACT

A light-emitting device having a structure in which a mask used for forming a film such as an organic compound layer does not come in contact with the pixels in forming the light-emitting elements, and a method of fabricating the same. In fabricating the light-emitting device of the active matrix type, a partitioning wall constituted by a second wiring and a separation portion is formed on the interlayer-insulating film, and the pixels are surrounded by the partitioning wall, preventing the mask from coming into direct contact with the pixels, the mask being used for forming the organic compound layer and the opposing electrode of the light-emitting elements.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of fabricating anactive matrix-type light-emitting device having a light-emitting elementon a substrate, and to a light-emitting device. The light-emittingelement stands for an element of a structure having an anode, a cathodeand an organic compound layer containing a light-emitting organicmaterial (hereinafter referred to as organic material) that produces EL(electroluminescence) sandwiched therebetween. The light-emittingelement referred to here is also called OLED (organic light-emittingdevice). In this specification, further, a light-emitting panel having alight-emitting element sealed between a substrate and a covering member,and a light-emitting module having an IC mounted on the light-emittingpanel, are generally referred to as light-emitting devices. Theinvention is further concerned with electric appliances using the abovelight-emitting device on the display unit. The EL (electroluminescent)devices referred to in this specification include triplet-based lightemission devices and/or singlet-based light emission devices, forexample.

[0003] 2. Prior Art

[0004] The light-emitting element is highly visible since it emits lightby itself, is best suited for decreasing the thickness since it does notuse backlight needed by the liquid crystal display devices (LCDs), andimposes no limitation on the viewing angle. In recent years, therefore,the light-emitting device using the light-emitting element is drawingattention to substitute for the CRTs and LCDs.

[0005] The light-emitting element includes a layer containing an organicmaterial that produces EL (electroluminescence: luminescence which isproduced upon the application of a electric field), an anode and acathode. The luminescence produced by the organic material can beclassified into emission of light (fluorescence) of when the singletexcitation state returns back to the ground state and emission of light(phosphorescence) of when the triplet excitation state returns back tothe ground state. The light-emitting device of the present invention mayuse the light-emitting element containing either organic material.

[0006] In this specification, the layers provided between the anode andthe cathode are all defined as organic compound layers. Concretelyspeaking, the organic compound layers include a light-emitting layer, apositive hole injection layer, an electron injection layer, a positivehole transporting layer and an electron transporting layer. Basically,the light-emitting element has a structure in which theanode/light-emitting layer/cathode are laminated in this order. Inaddition to this structure, the light-emitting element may often have astructure in which the anode/positive hole injectionlayer/light-emitting layer/cathode are laminated in this order or theanode/positive hole injection layer/light-emitting layer/electrontransporting layer/cathode are laminated in this order.

[0007] In forming the light-emitting element, the layer of the organiccompound is formed by the vaporization method, printing method, ink-jetmethod or spin-coating method.

[0008] Among them, the vaporization method capable of separatelyapplying the organic compound by using a metal mask or the like mask, isone of the film-forming methods frequently used for forming a film of alow-molecular organic material. In forming the active matrix-typelight-emitting element, however, this method arouses a problem in thatthe pixels are damaged when the metal mask comes in contact with thepixels in forming the film of the organic compound, since thelight-emitting elements are formed after the TFTs are formed.

[0009] According to the conventional method of fabricating thelight-emitting element as taught in Japanese Patent Laid-Open No.339968/1999, however, the passivation film is formed after the pixelelectrode is formed, and the organic compound layer and the opposingelectrode are formed after the passivation film is removed from thepixel electrode portion. Therefore, there has been formed a structurefor protection with the passivation film so that the metal mask will notcome in contact with the pixels. In this specification, the passivationfilm formed except on the pixel electrodes is called bank.

[0010] By forming the bank prior to forming the layer of the organiccompound and the opposing electrodes as described above, it is allowedto prevent the metal mask from coming into contact with the pixels.

[0011] In fabricating the light-emitting element, the bank comprising aninsulating material is formed to surround the pixels after the pixelelectrode is formed for each of the pixels.

[0012] The bank works not only to protect the wiring but also to protectthe pixel electrodes of the pixels, the organic compound layer and theopposing electrodes from being damaged when they are touched by themetal mask in forming the organic compound layer and the opposingelectrodes by vaporization on the pixel electrodes of the pixels byusing the metal mask, and to prevent the electrodes from beingshort-circuited to the wiring at the time when the opposing electrodesare formed.

[0013] However, formation of the bank requires another piece of mask forpatterning.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of this invention to provide a methodof fabricating an active matrix-type light-emitting device without thebank but which is provided with a function that substitutes for thebank, and a light-emitting device fabricated by this method.

[0015] This invention was accomplished in order to solve theabove-mentioned problem, and provides a method of fabricating an activematrix-type light-emitting device, wherein a structure for protectingthe surroundings of pixels is formed by using an interlayer-insulatingfilm and a wiring formed on the interlayer-insulating film, in order toprevent a metal mask from coming into direct contact with the pixels informing the light-emitting elements in the pixels.

[0016] Formation of the above structure makes it possible to control thepositions for forming the organic compound layer on the pixel electrodesand for forming the film on the opposing electrodes, so that theelectrodes forming the light-emitting elements will not beshort-circuited.

[0017] First, a TFT is formed on a substrate. In forming a gateelectrode of the TFT, there is simultaneously formed a first wiring on aportion of the region where the light-emitting element is to be formedto connect the TFT to a pixel electrode. In this specification, thefirst wiring is called electrode connection wiring. There is, then,formed an interlayer-insulating film of an insulating material. Uponpartly etching the interlayer-insulating film, the interlayer-insulatingfilm is also etched from a portion where a pixel is to be formed, andthe electrode connection wiring that has been formed is partly exposed.

[0018] Then, a metal film and an insulating film are formed. First, theinsulating film is patterned by dry etching. At this moment, the metalfilm and the insulating film provide sufficiently large selectionratios. Next, the metal film is patterned by wet etching thereby to forma separation portion and a wiring (second wiring) from the insulatingfilm and the metal film. In etching the metal film, the separationportion is simultaneously etched, too. Here, however, the materialforming the second wiring has been so selected as to be etched fasterwith an etching solution than the material forming the separationportion. If the substrate on which the TFT is formed after the secondwiring has been formed, is viewed from the upper side, therefore, thesecond wiring is formed having an area smaller than that of theseparation portion. The etching solution used for the wet etching may bea hydrofluoric acid or a mixed solution containing the hydrofluoricacid, or a mixed solution of phosphoric acid, nitric acid and aceticacid.

[0019] The second wiring is so formed as to be electrically connected tothe source or the drain of the TFT. The second wiring is further soformed as to be overlapped on the interlayer-insulating film and on partof the electrode connection wiring.

[0020] The wiring and the separation portion are thus formed on theinterlayer-insulating film. In this specification, the second wiring andthe separation portion formed on the interlayer-insulating film arecalled partitioning walls. In the foregoing was described the case wheredifferent etching methods were used for forming the separation portionand the second wiring, which, however, may be formed by the samewet-etching method. A current control TFT for controlling the amount ofcurrent flowing into the light-emitting element is in contact with theelectrode connection wiring and is electrically connected thereto.

[0021] After the partitioning walls have been formed, a pixel electrodeis formed for each of the pixels so as to be in contact with theelectrode connection wiring in a portion that is not overlapped on thesecond wiring. The pixel electrode formed here is not in contact withthe second wiring. An organic compound layer is deposited on the pixelelectrode by the vaporization method by using a metal mask.

[0022] Here, the metal mask may be so provided as will not come incontact with the substrate. Even when the metal mask is brought intocontact with the substrate, however, the pixels are not damaged. Due tothe metal mask and the partitioning wall, it is allowed to form theorganic compound layer at any desired position maintaining goodprecision.

[0023] Next, an opposing electrode is formed. Here, the electrode isformed with the partitioning walls as a mask, and is not short-circuitedto the pixel electrode or the wiring.

[0024] As described above, the bank is formed requiring no mask.Further, the light-emitting element is not deteriorated with water thatis produced at the time when the bank is formed using a resin, and thepixel electrode is not affected by the temperature at the time when thebank is fired. It is further allowed to form a structure in which thepixels are surrounded by the interlayer-insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIGS. 1(A) to 1(C) are views illustrating a method of fabricationaccording to this invention;

[0026] FIGS. 2(A) to 2(C) are views illustrating a method of fabricationaccording to this invention;

[0027] FIGS. 3(A) to 3(C) are views illustrating how to formpartitioning walls;

[0028]FIG. 4(A) is an SEM photograph of the partitioning walls;

[0029]FIG. 4(B) shows details of a structure shown in the SEM photographof FIG. 4(A);

[0030]FIG. 5 is a circuit diagram of pixels;

[0031]FIG. 6 is a circuit diagram of a pixel;

[0032] FIGS. 7(A) to 7(D) are views illustrating the steps offabrication;

[0033] FIGS. 8(A) to 8(C) are views illustrating the steps offabrication;

[0034] FIGS. 9(A) to 9(C) are views illustrating the steps offabrication;

[0035] FIGS. 10(A) and 10(B) are views illustrating a structure forsealing a light-emitting device;

[0036]FIG. 11(A) is a view illustrating a pixel unit and a driver;

[0037]FIG. 11(B) is a top view illustrating a part of a pixel unit;

[0038]FIG. 11(C) is a top view illustrating a part of a pixel unit; and

[0039] FIGS. 12(A) to 12(H) are views illustrating examples of electricappliances.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] An embodiment of the invention will now be described withreference to FIGS. 1 and 2. FIG. 1(A) illustrates a pixel which isformed in a plural number in a pixel unit.

[0041] First, an active layer of Si is formed on a substrate 100. Thisforms a source region, a drain region and a channel region of the TFTthat will be fabricated later. Here, regions surrounded by dotted linesin FIG. 1(A) are called region a (101 a) and region b (101 b). A TFTformed in the region a (101 a) serves as a switching TFT, and a TFTformed in the region b (101 b) serves as a current control TFT. That is,an active layer a (102 a) forms a source region, a drain region and achannel region of the switching TFT. Further, an active layer b (102 b)forms a source region, a drain region and a channel region of thecurrent control TFT.

[0042] Reference numeral 103 denotes a gate signal line, and a wiring104 connected to the gate signal line forms a gate electrode of theswitching TFT that will be formed later. Described here is a case wherethe device has a double gate structure. The gate structure, however, isin no way limited thereto only but may be a single-gate structure or amultiple-gate structure.

[0043] There is further formed, simultaneously with the above wirings, adrain wiring a (105) which is electrically connected to the drain of theswitching TFT. The drain wiring a (105) serves as a gate electrode ofthe current control TFT. There is further formed a current feeder line106 that forms an electric connection to the current control TFT. Thecurrent feeder line 106 feeds an electric current that flows into thelight-emitting element.

[0044] Reference numeral 107 denotes an electrode connection wiring thatelectrically connects the current control TFT and the pixel electrodetogether.

[0045] After these wirings are formed, an interlayer-insulating film 108is formed. An insulating material is used for forming theinterlayer-insulating film 108. Concretely speaking, there may be usedan inorganic film containing silicon, such as silicon oxide or siliconnitride, or an organic resin film such as of polyimide, polyamide oracrylic resin.

[0046] After the interlayer-insulating film 108 is formed, the regionfor forming the pixel electrode is patterned into a shape as shown inFIG. 1(B). Here, as shown, the interlayer-insulating film has beenformed to partly cover the electrode wiring 107.

[0047]FIG. 1(C) is a sectional view of a portion along a dotted line AA′in FIG. 1(B). Namely, in this portion, the wirings are all covered withthe interlayer-insulating film 108.

[0048] Next, in addition to a source signal line 109, there are formed asource wiring a (110) for electrically connecting the current controlTFT to the current feeder line 106, and a drain wiring b (111) forelectrically connecting the drain of the current control TFT to theelectrode connection wiring 107 (FIG. 2(A)).

[0049] These wirings are formed by forming the structure shown in FIG.1(B) and, then, forming a film of a metal material for forming thewirings. The metal material used here may be Al (aluminum) or Ti(titanium), or an alloy of Al and Ti, or an alloy of Al and Si.

[0050] On the metal film is further formed a separation film by using amaterial which provides a selection ratio with the etching solution whenit is etched simultaneously with the metal film by the wet-etchingmethod. As described above, the separation film may be formed using anymaterial provided it exhibits a selection ratio to the metal film at thetime of wet etching. Therefore, the separation film may be an inorganicfilm such as of silicon nitride or silicon oxide, or may be a metal filmsuch as of Ti. There may be further used an organic resin such aspolyimide, polyamide, acrylic resin or resist.

[0051] A wiring pattern is formed after the metal film and theseparation film are formed. Dry etching is effected after the separationfilm is patterned, thereby to form a wiring pattern of the metal filmand the separation film laminated one upon the other. The wiring iswet-etched to etch the metal film having a larger selection ratio ofetching. When viewed from the upper side, therefore, the metal filmbecomes smaller than the separation film as shown in FIG. 2(A).

[0052] Here, a portion along the dotted line AA′ in FIG. 2(A) ispatterned, i.e., the metal film is patterned to form a drain wiring b(111). FIG. 2(B) is a sectional view of a separation portion 112 formedby etching the separation film. In this specification, the separationfilms formed on the wiring by patterning are all called separationportions. FIG. 2(B) illustrates a state where the separation portion 112is formed on the drain wiring b (111). In this invention, however, thewirings formed by patterning the separation film all have their upperportions covered with the separation portion.

[0053]FIG. 2(C) is a sectional view of a portion along a dotted line BB′in FIG. 2(A). As will be understood from the sectional view of FIG.2(C), the electrode connection wiring 107 is formed being partlyconnected to the drain wiring b (111) and is, hence, electricallyconnected thereto.

[0054] In a region c (113) shown in FIG. 2(C), the pixel electrode forforming the light-emitting element is patterned, and an organic compoundlayer and an opposing electrode are formed thereon by vaporization byusing a metal mask. Here, due to the partitioning wall formed by thedrain wiring b (111) and the separation portion 112, it is allowed toprevent the pixel from coming in contact with the metal mask. It isfurther made possible to solve the problem of short-circuit between thepixel electrode and the opposing electrode caused by the positions forforming the organic compound layer and the opposing electrode.

[0055] Further, since the drain wiring b (111) has its upper partcompletely covered with the separation portion 112, the problem ofshort-circuit between the drain wiring b (111) and the opposingelectrode is prevented at the time when the opposing electrode is formedfor forming the light-emitting element.

[0056] Upon putting the invention into practice as described above, thewiring can be used to substitute for the conventional bank. Therefore,no mask needs to be used for forming the bank, and the process offabrication can be simplified.

[0057] Described below are the method of forming the wiring and theseparation portion by etching described above, and the shapes thereof.

[0058] Referring to FIG. 3(A), a metal film 201 is formed on a substrate200, and a separation film 202 is formed on the metal film 201. FIG.3(a) is a sectional view along a dotted line AA′ in FIG. 3(A).

[0059] The separation film 202 is patterned by dry etching by using aresist 203 to form a separation portion 204 having a desired pattern asshown in FIG. 3(B).

[0060]FIG. 3(b) illustrates the sectional structure along a dotted lineAA′ in FIG. 3(B).

[0061] Here, the metal film 201 is etched by wet etching. At thismoment, the material forming the separation portion 204 and the materialforming the metal film 201 must be those that are capable of providing asufficient degree of selection ratio for the etching solution during theetching.

[0062] Here, the metal film 201 is etched to form a separation portion204 and a wiring 205 as shown in FIG. 3(C). FIG. 3(c) shows thesectional structure along a dotted line AA′ in FIG. 3(C).

[0063]FIG. 4(A) is an SEM photograph of the sectional structures of theseparation portion 204 and the wiring 205 formed by the above method byusing Al as the metal film 201 and SiN as the separation portion 204.

[0064]FIG. 4(B) illustrates in detail the structure shown in the SEMphotograph of FIG. 4(A). Reference numerals used here are correspondingto reference numerals used in FIG. 3.

[0065] Here, the etching is isotropic in which a thickness (x) of thewiring, an etching distance (y) of the upper part of the wiring in thetransverse direction with the etching center (c) as a reference, and anetching distance (a) of a lower part of the wiring in the transversedirection with the etching center (c) as a reference, satisfy arelationship y=x+α(α>0). In the case of this embodiment, the thickness xof the wiring is 500 nm, the etching distance a of the lower part of thewiring in the transverse direction is 400 nm, and the etching distance yof the upper part of the wiring in the transverse direction is 900 nm.Not being limited thereto only according to this invention, further, thewiring material, the width of wiring and the etching rate may besuitably adjusted such that the above relationship holds true.

EXAMPLES Example 1

[0066] This Example deals with the structure of a pixel unit of alight-emitting device fabricated according to this invention.

[0067]FIG. 5 is a diagram illustrating, on an enlarged scale, a pixelunit 301 of the light-emitting device. The pixel unit 301 is providedwith source signal lines (S1 to Sx), current feeder lines (V1 to Vx) andgate signal lines (G1 to Gy).

[0068] In the case of this Example, a pixel 304 is a region having anyone of the source signal lines (S1 to Sx), any one of the current feederlines (V1 to Vx) and any one of the gate signal lines (G1 to Gy). Thepixel unit 301 includes plural pixels 304 arranged in the form of amatrix.

[0069] Referring to FIG. 6 illustrating the pixel 304 on an enlargedscale, reference numeral 305 denotes a switching TFT. The gate electrodeof the switching TFT 305 is connected to the gate signal line G (G1 toGx). The switching TFT 305 has the source region and the drain region,the one of which being connected to the source signal line S (S1 to Sx)and the other one of which being connected to the gate electrode of acurrent control TFT 306 and to a capacitor 308 possessed by each pixel.

[0070] The capacitor 308 is for holding the gate voltage (potentialdifference between the gate electrode and the source region) of thecurrent control TFT 306 when the switching TFT 305 is in thenon-selected state (off state). This Example illustrates theconstitution provided with the capacitor 308. Being not limited to thisconstitution only, however, the invention may not be provided with thecapacitor 308.

[0071] The current control TFT 306 includes the source region and thedrain region, the one of which being connected to the current feederline V (V1 to Vx) and the other one of which being connected to alight-emitting element 307. The current feeder line V is connected tothe capacitor 308.

[0072] The light-emitting element 307 includes an anode, a cathode andan organic compound layer provided between the anode and the cathode.When the anode is connected to the source region or the drain region ofthe current control TFT 306, the anode serves as the pixel electrode andthe cathode serves as the opposing electrode. Conversely, when thecathode is connected to the source region or to the drain region of thecurrent control TFT 306, the cathode serves as the pixel electrode andthe anode serves as the opposing electrode.

[0073] An opposing potential is applied to the opposing electrode of thelight-emitting element 307. A power source potential is applied to thecurrent feeder line V. The power source potential and the opposingpotential are given from a power source such as of an IC providedoutside the light-emitting device of the invention.

[0074] The switching TFT 305 and the current control TFT 306 may beeither the n-channel TFTs or the p-channel TFTs. Here, however, wheneither the source region or the drain region of the current control TFT306 is connected to the anode of the light-emitting element 307, it isdesired that the current control TFT 306 is the p-channel TFT. Further,when either the source region or the drain region of the current controlTFT 306 is connected to the cathode of the light-emitting element 307,it is desired that the current control TFT 306 is the n-channel TFT.

[0075] Further, the switching TFT 305 and the current control TFT 306may have a multi-gate structure such as a double-gate structure or atriple-gate structure instead of the single-gate structure.

[0076] Next, described with reference to FIGS. 7 to 9 is a method ofsimultaneously forming, on the same substrate, the pixel unit describedabove and the TFTs (n-channel TFTs and p-channel TFTs) of a drivecircuit provided surrounding the pixel unit.

[0077] This Example uses a substrate 900 of a glass such as bariumborosilicate glass or aluminoborosilicate glass as represented by theglass #7059 or the glass #1737 of Corning Co. There is no limitation onthe substrate 900 provided it has a property of transmitting light, andthere maybe used a quartz substrate. There may be further used a plasticsubstrate having heat resistance capable of withstanding the treatmenttemperature of this Example.

[0078] Referring next to FIG. 7(A), an underlying film 901 comprising aninsulating film such as silicon oxide film, silicon nitride film orsilicon oxynitride film is formed on the substrate 900. In this Example,the underlying film 901 has a two-layer structure. There, however, maybe employed a structure in which a single layer or two or more layersare laminated on the insulating film. The first layer of the underlyingfilm 901 is a silicon oxynitride film 901 a formed maintaining athickness of from 10 to 200 nm (preferably, from 50 to 100 nm) relyingupon a plasma CVD method by using SiH₄, NH₃ and N₂O as reaction gases.In this Example, the silicon oxynitride film 901 a (having a compositionratio of Si=32%, O=27%, N=24%, H=17%) is formed maintaining a thicknessof 50 nm. The second layer of the underlying film 901 is a siliconoxynitride film 901 b formed maintaining a thickness of from 50 to 200nm (preferably, from 100 to 150 nm) relying upon the plasma CVD methodby using SiH₄ and N₂O as reaction gases. In this Example, the siliconoxynitride film 901 b (having a composition ratio of Si=32%, O=59%,N=7%, H=2%) is formed maintaining a thickness of 100 nm.

[0079] Then, semiconductor layers 902 to 905 are formed on theunderlying film 901. The semiconductor layers 902 to 905 are formed byforming a semiconductor film having an amorphous structure by a knownmeans (sputtering method, LPCVD method or plasma CVD method) followed bya known crystallization processing (laser crystallization method, heatcrystallization method or heat crystallization method using a catalystsuch as nickel), and patterning the crystalline semiconductor film thusobtained into a desired shape. The semiconductor layers 902 to 905 areformed in a thickness of from 25 to 80 nm (preferably, from 30 to 60nm). Though there is no limitation on the material of the crystallinesemiconductor film, there is preferably used silicon or asilicon-germanium (Si_(x)Ge_(1-x) (X=0.0001 to 0.02)) alloy. In thisExample, the amorphous silicon film is formed maintaining a thickness of55 nm relying on the plasma CVD method and, then, a solution containingnickel is held on the amorphous silicon film. The amorphous silicon filmis dehydrogenated (500° C., one hour), heat-crystallized (550° C., 4hours) and is, further, subjected to the laser annealing to improve thecrystallization, thereby to form a crystalline silicon film. Thecrystalline silicon film is patterned by the photolithographic method toform semiconductor layers 902 to 905.

[0080] The semiconductor layers 902 to 905 that have been formed mayfurther be doped with trace amounts of an impurity element (boron orphosphorus) to control the threshold value of the TFT.

[0081] Informing the crystalline semiconductor film by the lasercrystallization method, further, there may be employed an excimer laserof the pulse oscillation type or of the continuously light-emittingtype, a YAG laser or a YVO₄ laser. When these lasers are to be used, itis desired that a laser beam emitted from a laser oscillator is focusedinto a line through an optical system so as to fall on the semiconductorfilm. The conditions for crystallization are suitably selected by aperson who carries out the process. When the excimer laser is used, thepulse oscillation frequency is set to be 300 Hz and the laser energydensity to be from 100 to 400 mJ/cm² (typically, from 200 to 300mJ/cm²). When the YAG laser is used, the pulse oscillation frequency isset to be from 30 to 300 kHz by utilizing the second harmonics and thelaser energy density to be from 300 to 600 mJ/cm² (typically, from 350to 500 mJ/cm²). The whole surface of the substrate is irradiated withthe laser beam focused into a line of a width of 100 to 1000 μm, forExample, 400 μm, and the overlapping ratio of the linear beam at thismoment is set to be 50 to 90%.

[0082] Then, a gate-insulating film 906 is formed to cover thesemiconductor layers 902 to 905. The gate-insulating film 906 is formedof an insulating film containing silicon maintaining a thickness of from40 to 150 nm by the plasma CVD method or the sputtering method. In thisExample, the gate-insulating film is formed of a silicon oxynitride film(composition ratio of Si=32%, O=59%, N=7%, H=2%) maintaining a thicknessof 110 nm by the plasma CVD method. The gate-insulating film is notlimited to the silicon oxynitride film but may have a structure on whichis laminated a single layer or plural layers of an insulating filmcontaining silicon.

[0083] When the silicon oxide film is to be formed, TEOS (tetraethylorthosilicate) and O₂ are mixed together by the plasma CVD method, andare reacted together under a reaction pressure of 40 Pa, at a substratetemperature of from 300 to 400° C., at a frequency of 13.56 MHz and adischarge electric power density of from 0.5 to 0.8 W/cm². The thusformed silicon oxide film is, then, heat-annealed at 400 to 500° C.thereby to obtain the gate-insulating film having good properties.

[0084] Then, a heat-resistant electrically conducting layer 907 isformed on the gate-insulating film 906 maintaining a thickness of from200 to 400 nm (preferably, from 250 to 350 nm) to form the gateelectrode. The heat-resistant electrically conducting layer 907 may beformed as a single layer or may, as required, be formed in a structureof laminated layers of plural layers such as two layers or three layers.The heat-resistant electrically conducting layer contains an elementselected from Ta, Ti and W, or contains an alloy of the above element,or an alloy of a combination of the above elements. The heat-resistantelectrically conducting layer is formed by the sputtering method or theCVD method, and should contain impurities at a decreased concentrationto decrease the resistance and should, particularly, contain oxygen at aconcentration of not higher than 30 ppm. In this Example, the W film isformed maintaining a thickness of 300 nm. The W film may be formed bythe sputtering method by using W as a target, or may be formed by thehot CVD method by using tungsten hexafluoride (WF₆). In either case, itis necessary to decrease the resistance so that it can be used as thegate electrode. It is, therefore, desired that the W film has aresistivity of not larger than 20 μΩcm. The resistance of the W film canbe decreased by coarsening the crystalline particles. When W containsmuch impurity elements such as oxygen, the crystallization is impairedand the resistance increases. When the sputtering method is employed,therefore, a W target having a purity of 99.9999% is used, and the Wfilm is formed while giving a sufficient degree of attention so that theimpurities will not be infiltrated from the gaseous phase during theformation of the film, to realize the resistivity of from 9 to 20 μΩcm.

[0085] On the other hand, the Ta film that is used as the heat-resistantelectrically conducting layer 907 can similarly be formed by thesputtering method. The Ta film is formed by using Ar as a sputteringgas. Further, the addition of suitable amounts of Xe and Kr into the gasduring the sputtering makes it possible to relax the internal stress ofthe film that is formed and to prevent the film from being peeled off.The Ta film of a phase has a resistivity of about 20 μΩcm and can beused as the gate electrode but the Ta film of β phase has a resistivityof about 180 μΩcm and is not suited for use as the gate electrode. TheTaN film has a crystalline structure close to the a phase. Therefore, ifthe TaN film is formed under the Ta film, there is easily formed the Tafilm of α-phase. Further, though not diagramed, formation of the siliconfilm doped with phosphorus (P) maintaining a thickness of about 2 toabout 20 nm under the heat-resistant electrically conducting layer 907is effective in fabricating the device. This helps improve the intimateadhesion of the electrically conducting film formed thereon, prevent theoxidation, and prevent trace amounts of alkali metal elements containedin the heat-resistant electrically conducting layer 907 from beingdiffused into the gate-insulating film 906 of the first shape. In anyway, it is desired that the heat-resistant electrically conducting layer907 has a resistivity over a range of from 10 to 50 μΩcm.

[0086] Next, a mask 908 is formed by a resist relying upon thephotolithographic technology. Then, a first etching is executed. ThisExample uses an ICP etching device, uses Cl₂ and CF₄ as etching gases,and forms a plasma with RF (13.56 MHz) electric power of 3.2 W/cm² undera pressure of 1 Pa. The RF (13.56 MHz) electric power of 224 mW/cm² issupplied to the side of the substrate (sample stage), too, whereby asubstantially negative self-bias voltage is applied. Under thiscondition, the W film is etched at a rate of about 100 nm/min. The firstetching treatment is effected by estimating the time by which the W filmis just etched relying upon this etching rate, and is conducted for aperiod of time which is 20% longer than the estimated etching time.

[0087] The electrically conducting layers 909 to 912 having a firsttapered shape are formed by the first etching treatment. Theelectrically conducting layers 909 to 912 are tapered at an angle offrom 15 to 300. To execute the etching without leaving residue,over-etching is conducted by increasing the etching time by about 10 to20%. The selection ratio of the silicon oxynitride film (gate-insulatingfilm 906) to the W film is 2 to 4 (typically, 3). Due to theover-etching, therefore, the surface where the silicon oxynitride filmis exposed is etched by about 20 to about 50 nm (FIG. 7(B)).

[0088] Then, a first doping treatment is effected to add an impurityelement of a first type of electric conduction to the semiconductorlayer. Here, a step is conducted to add an impurity element forimparting the n-type. A mask 908 forming the electrically conductinglayer of a first shape is left, and an impurity element is added by theion-doping method to impart the n-type in a self-aligned manner with theelectrically conducting layers 909 to 912 having a first tapered shapeas masks. The dosage is set to be from 1×10¹³ to 5×10¹⁴ atoms/cm² sothat the impurity element for imparting the n-type reaches theunderlying semiconductor layer penetrating through the tapered portionand the gate-insulating film 906 at the ends of the gate electrode, andthe acceleration voltage is selected to be from 80 to 160 keV. As theimpurity element for imparting the n-type, there is used an elementbelonging to the Group 15 and, typically, phosphorus (P) or arsenic(As). Phosphorus (P) is used, here. Due to the ion-doping method, animpurity element for imparting the n-type is added to the first impurityregions 914 to 917 over a concentration range of from 1×10²⁰ to 1×10²¹atoms/cm³ (FIG. 7(C)).

[0089] In this step, the impurities turn down to the lower side of theelectrically conducting layers 909 to 912 of the first shape dependingupon the doping conditions, and it often happens that the first impurityregions 914 to 917 are overlapped on the electrically conducting layers909 to 912 of the first shape.

[0090] Next, the second etching treatment is conducted as shown in FIG.7(D). The etching treatment, too, is conducted by using the ICP etchingdevice, using a mixed gas of CF₄ and Cl₂ as an etching gas, using an RFelectric power of 3.2 W/cm² (13.56 MHz), a bias power of 45 mW/cm²(13.56 MHz) under a pressure of 1.0 Pa. Under this condition, there areformed the electrically conducting layers 918 to 921 of a second shape.The end portions thereof are tapered, and the thicknesses graduallyincrease from the ends toward the inside. The rate of isotropic etchingincreases in proportion to a decrease in the bias voltage applied to theside of the substrate as compared to the first etching treatment, andthe angle of the tapered portions becomes 30 to 600. The mask 908 isground at the edge by etching to form a mask 922. In the step of FIG.7(D), the surface of the gate-insulating film 906 is etched by about 40nm.

[0091] Then, the doping is effected with an impurity element forimparting the n-type under the condition of an increased accelerationvoltage by decreasing the dosage to be smaller than that of the firstdoping treatment. For Example, the acceleration voltage is set to befrom 70 to 120 keV, the dosage is set to be 1×10¹³/cm² thereby to formfirst impurity regions 924 to 927 having an increased impurityconcentration, and second impurity regions 928 to 931 that are incontact with the first impurity regions 924 to 927. In this step, theimpurity may turn down to the lower side of the electrically conductinglayers 918 to 921 of the second shape, and the second impurity regions928 to 931 may be overlapped on the electrically conducting layers 918to 921 of the second shape. The impurity concentration in the secondimpurity regions is from 1×10¹⁶ to 1×10¹⁸ atoms/cm³ (FIG. 8(A)).

[0092] Referring to FIG. 8(B), impurity regions 933 (933 a, 933 b) and934 (934 a, 934 b) of the conduction type opposite to the one conductiontype are formed in the semiconductor layers 902, 905 that form thep-channel TFTs. In this case, too, an impurity element for imparting thep-type is added using the electrically conducting layers 918, 921 of thesecond shape as masks to form impurity regions in a self-aligned manner.At this moment, the semiconductor layers 903 and 904 forming then-channel TFTs are entirely covered for their surfaces by forming a mask932 of a resist. Here, the impurity regions 933 and 934 are formed bythe ion-doping method by using diborane (B₂H₆). The impurity element forimparting the p-type is added to the impurity regions 933 and 934 at aconcentration of from 2×10²⁰ to 2×10²¹ atoms/cm³.

[0093] If closely considered, however, the impurity regions 933, 934 canbe divided into two regions containing an impurity element that impartsthe n-type. Third impurity regions 933 a and 934 a contain the impurityelement that imparts the n-type at a concentration of from 1×10²⁰ to1×10²¹ atoms/cm³ and fourth impurity regions 933 b and 934 b contain theimpurity element that imparts the n-type at a concentration of from1×10¹⁷ to 1×10²⁰ atoms/cm³. In the impurity regions 933 b and 934 b,however, the impurity element for imparting the p-type is contained at aconcentration of not smaller than 1×10¹⁹ atoms/cm³ and in the thirdimpurity regions 933 a and 934 a, the impurity element for imparting thep-type is contained at a concentration which is 1.5 to 3 times as highas the concentration of the impurity element for imparting the n-type.Therefore, the third impurity regions work as source regions and drainregions of the p-channel TFTs without arousing any problem.

[0094] Referring next to FIG. 8(C), a first interlayer-insulating film937 is formed on the electrically conducting layers 918 to 921 of thesecond shape and on the gate-insulating film 906. The firstinterlayer-insulating film 937 may be formed of a silicon oxide film, asilicon oxynitride film, a silicon nitride film, or a laminated-layerfilm of a combination thereof. In any case, the firstinterlayer-insulating film 937 is formed of an inorganic insulatingmaterial. The first interlayer-insulating film 937 has a thickness of100 to 200 nm. When the silicon oxide film is used as the firstinterlayer-insulating film 937, TEOS and O₂ are mixed together by theplasma CVD method, and are reacted together under a pressure of 40 Pa ata substrate temperature of 300 to 400° C. while discharging the electricpower at a high frequency (13.56 MHz) and at a power density of 0.5 to0.8 W/cm². When the silicon oxynitride film is used as the firstinterlayer-insulating film 937, this silicon oxynitride film may beformed from SiH₄, N₂O and NH₃, or from SiH₄ and N₂O by the plasma CVDmethod. The conditions of formation in this case are a reaction pressureof from 20 to 200 Pa, a substrate temperature of from 300 to 400° C. anda high-frequency (60 MHz) power density of from 0.1 to 1.0 W/cm². As thefirst interlayer-insulating film 937, further, there may be used ahydrogenated silicon oxynitride film formed by using SiH₄, N₂O and H₂.The silicon nitride film, too, can similarly be formed by using SiH₄ andNH₃ by the plasma CVD method.

[0095] Then, a step is conducted for activating the impurity elementsthat impart the n-type and the p-type added at their respectiveconcentrations. This step is conducted by thermal annealing method usingan annealing furnace. There can be further employed a laser annealingmethod or a rapid thermal annealing method (RTA method). The thermalannealing method is conducted in a nitrogen atmosphere containing oxygenat a concentration of not higher than 1 ppm and, preferably, not higherthan 0.1 ppm at from 400 to 700° C. and, typically, at from 500 to 600°C. In this Example, the heat treatment is conducted at 550° C. for 4hours. When a plastic substrate having a low heat-resistance temperatureis used as the substrate 501, it is desired to employ the laserannealing method.

[0096] Following the step of activation, the atmospheric gas is changed,and the heat treatment is conducted in an atmosphere containing 3 to100% of hydrogen at from 300 to 450° C. for from 1 to 12 hours tohydrogenate the semiconductor layer. This step is to terminate thedangling bonds of 10¹⁶ to 10¹⁸/cm³ in the semiconductor layer withhydrogen that is thermally excited. As another means of hydrogenation,the plasma hydrogenation may be executed (using hydrogen excited withplasma). In any way, it is desired that the defect density in thesemiconductor layers 902 to 905 is suppressed to be not larger than10¹⁶/cm³. For this purpose, hydrogen may be added in an amount of from0.01 to 0.1 atomic %.

[0097] Then, a second interlayer-insulating film 939 of an organicinsulating material is formed maintaining an average thickness of from1.0 to 2.0 μm. As the organic resin material, there can be usedpolyimide, acrylic resin, polyamide, polyimideamide, BCB(benzocyclobutene) as well as photosensitive acrylic resin. When thereis used, for example, a polyimide of the type that is heat-polymerizedafter being applied onto the substrate, the second interlayer-insulatingfilm is formed being fired in a clean oven at 300° C. When there is usedan acrylic resin, there is used the one of the two-can type. Namely, themain material and a curing agent are mixed together, applied onto thewhole surface of the substrate by using a spinner, pre-heated by using ahot plate at 80° C. for 60 seconds, and are fired at 250° C. for 60minutes in a clean oven to form the second interlayer-insulating film.

[0098] Thus, the second interlayer-insulating film 939 is formed byusing an organic insulating material featuring good and flattenedsurface. Further, the organic resin material, in general, has a smalldielectric constant and lowers the parasitic capacitance. The organicresin material, however, is hygroscopic and is not suited as aprotection film. It is, therefore, desired that the secondinterlayer-insulating film is used in combination with the silicon oxidefilm, silicon oxynitride film or silicon nitride film formed as thefirst interlayer-insulating film 937.

[0099] Thereafter, the resist mask of a predetermined pattern is formed,and contact holes are formed in the semiconductor layers to reach theimpurity regions serving as source regions or drain regions. The contactholes are formed by dry etching. In this case, a mixed gas of CF₄, O₂and He is used as the etching gas to, first, etch the secondinterlayer-insulating film 939 of the organic resin material.Thereafter, CF₄ and O₂ are used as the etching gas to etch the firstinterlayer-insulating film 937. In order to further enhance theselection ratio relative to the semiconductor layer, CHF₃ is used as theetching gas to etch the gate-insulating film 906, thereby to form thecontact holes.

[0100] Then, a wiring layer 940 formed of an electrically conductingmetal film is formed by sputtering or vacuum vaporization. On the wiringlayer 940 is further formed a separation layer 941 of a material whichprovides a large selection ratio for the wiring layer and for theetching solution during the etching. The separation layer 941 may beformed of an inorganic material such as nitride film or oxide film, ormay be formed of an organic resin such as polyimide, polyamide or BCB(benzocyclobutene). Or, the separation layer 941 may be formed of ametal material.

[0101] Here, the separation layer 941 is patterned by using a mask andis, then, etched to form source wirings 942 a to 945 a, drain wirings946 a to 948 a and separation portions 942 b to 948 b. In thisspecification, the structure formed by the separation layer and thewiring is called partitioning wall. Further, though not diagramed inthis Example, the wiring is formed by a laminate of a 50 nm-thick Tifilm and a 500 nm-thick alloy film (alloy film of Al and Ti).

[0102] Then, a transparent electrically conducting film is formedthereon maintaining a thickness of 80 to 120 nm, and is patterned toform a pixel electrode 949 (FIG. 9(B)). In this Example, the pixelelectrode 949 works as the anode. Therefore, the pixel electrode 949 isformed by using an indium oxide-tin (ITO) film or a transparentelectrically conducting film obtained by mixing 2 to 20% of a zinc oxide(ZnO) into indium oxide.

[0103] Further, the pixel electrode 949 is formed being in contact with,and overlapped on, the contact wiring 923 that is electrically connectedto the drain wiring 946 a, so that the pixel electrode 949 iselectrically connected with the drain region of the current control TFT963.

[0104] Referring next to FIG. 9(B), an organic compound layer 950, acathode 951 which is an opposing electrode and a passivation film 952are formed by the evaporation method. It is here desired that the pixelelectrode 947 is heat-treated to completely remove the water contentprior to forming the organic compound layer 950. In this Example, anelectrode formed of a Mg:Ag alloy is used as the cathode of thelight-emitting element, though any other material may be used, as amatter of course.

[0105] The organic compound layer 950 is formed by laminating plurallayers such as a positive hole injection layer, a positive holetransporting layer, an electron transporting layer, an electroninjection layer and a buffer layer in addition to the light-emittinglayer. The structure of the organic compound layer 950 used in thisExample will now be described in detail.

[0106] In this Example, the positive hole injection layer is formed bydepositing copper phthalocyanine, and the positive hole transportinglayer is formed by depositing MTDATA (4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine) by the evaporationmethod. It is, however, also allowable to use a PEDOT which is apolythiophene derivative as the positive hole injection layer, and anα-NPD or a polyphenylenevinylene (PPV) as the positive hole transportinglayer.

[0107] Next, a light-emitting layer is formed. In this Example, organiccompound layers that emit different light are formed by using differentmaterials for the light-emitting layers. In this Example, organiccompound layers are formed to emit light of red, green and blue colors.

[0108] The light-emitting layer that emits light of red color is formedby doping Alq₃ with DCM. There can be further used an Eu complex(Eu(DCM)₃(Phen)) and aluminum quinolylato complex (Alq₃) doped withDCM-1, as well as any other known material.

[0109] The light-emitting layer that emits light of green color isformed by depositing CBP and Ir(ppy)₃ together. There can be furtherused an aluminum quinolylato complex (Alq₃) andbenzoquinolynolatoberyllium complex (BeBq). There can be further usedthe aluminum quinolylato complex (Alq₃) being doped with cumarin 6 orquinacridone, as well as any other known material.

[0110] As the light-emitting layer that emits light of blue color, therecan be used DPVBi which is a distyryl derivative or a zinc complexhaving an azomethine compound as a ligand and the DPVBi doped withperylene, as well as any other known material.

[0111] After the light-emitting layer is formed, further, there may beformed the electron transporting layer and the electron injection layer.In this embodiment, a material such as 1,3,4-oxadiazole derivative or1,2,4-triazole derivative (TAZ) is used as the electron transportinglayer. Further, a buffer layer 206 may be formed by using such amaterial as lithium fluoride (LiF), aluminum oxide (Al₂O₃) orlithiumacetyl acetonate (Liacac).

[0112] The organic compound layer 950 having the laminated-layerstructure may have a thickness of from 10 to 400 [nm] (typically, from60 to 150 [nm]), and the cathode 951 may have a thickness of from 80 to200 [nm](typically, from 100 to 150 [nm]).

[0113] After the organic compound layer 950 is formed, the cathode 951is formed by the vaporization method to complete the light-emittingelement 954. In this Example, the Mg:Ag alloy is used as theelectrically conducting film that serves as the cathode 951 of thelight-emitting element 954. It is, however, also allowable to form anAl—Li alloy film (alloy film of aluminum and lithium) or a film formedby covaporizing aluminum and an element belonging to the Group 1 or theGroup 2 of periodic table. The covaporization stands for thevaporization method by which the cells for being vaporized are heatedtogether and different substances are mixed together in the step offorming the film.

[0114] After the cathode 951 has been formed, a passivation film 952 isformed. Upon forming the passivation film 952, the organic compoundlayer 950 and the cathode 951 can be protected from the water componentand oxygen. In this Example, a silicon nitride film is formedmaintaining a thickness of 300 nm as the passivation film 952. After thecathode 951 is formed, the passivation film 952 may be continuouslyformed without being exposed to the open air.

[0115] Thus, the light-emitting device of the structure shown in FIG.9(C) is completed. A portion where the pixel electrode 949, the organiccompound layer 950 and the cathode 951 are overlapped one upon theother, corresponds to the light-emitting element 954.

[0116] The p-channel TFT 960 and the n-channel TFT 961 are the TFTspossessed by the drive circuit, and are forming a CMOS. The switchingTFT 962 and the current control TFT 963 are the TFTs possessed by thepixel unit. The TFTs of the drive circuit and the TFTs of the pixel unitcan be formed on the same substrate.

[0117] In the case of the light-emitting device using the light-emittingelement, the power source voltage of the drive circuit is about 5 toabout 6 V, and is about 10 V at the greatest. Therefore, the TFTs arenot much deteriorated by hot electrons. Further, since the drive circuitneeds to be operated at a high speed, it is desired that the gatecapacity of the TFT is better small. In the drive circuit for thelight-emitting device using light-emitting elements as in this Example,therefore, it is desired that the second impurity region 929 and thefourth impurity region 933 b possessed by the semiconductor layer of theTFT are not overlapped on the gate electrodes 918 and 919.

[0118] Thus, there is formed a light-emitting panel forming thelight-emitting elements on the substrate as shown in FIG. 9(C).

[0119] The thus formed light-emitting panel is then sealed and iselectrically connected to an external power source through an FPC tocomplete the light-emitting device of the invention.

Example 2

[0120] This Example deals in detail with reference to FIG. 10 the methodof completing, as the light-emitting device, the light-emitting panelfabricated up to FIG. 9(C) in Example 1.

[0121]FIG. 10(A) is a top view illustrating a state where thelight-emitting element is sealed, and FIG. 10(B) is a sectional view ofwhen FIG. 10(A) is cut along the line A-A′. A dotted line 1001 denotes adrive circuit of the source side, 1002 denotes a pixel unit, and 1003denotes a drive circuit of the gate side. Reference numeral 1004 denotesa covering member, 1005 denotes a sealing agent, and space 1007 isformed on the inside surrounded by the sealing agent 1005.

[0122] Reference numeral 1008 denotes a wiring for transmitting thesignals input to the drive circuit 1001 of the source side and to thedrive circuit 1003 of the gate side, and video signals and clock signalsare received through an FPC (flexible printed circuit) that serves as anexternal input terminal. Though the FPC only is diagramed here, aprinted wiring board (PWB) may be mounted on the FPC. In thisspecification, the light-emitting device includes not only thelight-emitting module of a state of mounting the FPC or the PWB on thelight-emitting panel but also the light-emitting module mounting an IC.

[0123] Next, the sectional structure will be described with reference toFIG. 10(B). The pixel unit 1002 and the drive circuit 1003 on the gateside are formed on the substrate 1000, the pixel unit 1002 beingconstituted by current control TFTs 1011 and plural pixels containingtransparent electrodes 1012 electrically connected to the drains of thecurrent control TFTs 1011. Further, the drive circuit 1003 of the gateside is constituted by the CMOS circuit of a combination of then-channel TFTs 1013 and the p-channel TFTs 1014 (see FIG. 9).

[0124] The pixel electrode 1012 serves as the anode of thelight-emitting element. Interlayer-insulating films 1006 are formed atboth ends of the pixel electrode 1012. On the pixel electrode 1012 areformed an organic compound layer 1016 and a cathode 1017 which is anopposing electrode of the light-emitting element.

[0125] The cathode 1017 also works as a wiring common to plural pixels,and is electrically connected to the FPC 1010 through the connectionwiring 1009. The elements included in the pixel unit 1002 and in thedrive circuit 1003 of the gate side are all covered with the passivationfilm 1018.

[0126] The covering member 1004 is stuck with the sealing agent 1005.There may be provided a spacer of a plastic film to secure a gap betweenthe covering member 1004 and the light-emitting element. Closed space isdefined on the inside of the sealing agent 1005, and is filled with aninert gas such as nitrogen or argon gas. A hygroscopic member asrepresented by barium oxide may be provided in the sealed space.

[0127] As the covering member 1004, there can be used a glass, ceramics,plastics or a metal. Here, however, the covering member 1004 must becapable of transmitting light when light is to be emitted on the side ofthe covering member 1004. As the plastics, there can be used FRP(fiberglass-reinforced plastics), PVF (polyvinyl fluoride), Mylar,polyester or acrylic resin.

[0128] As described above, the light-emitting panel is sealed by usingthe covering member 1004 and the sealing agent 1005, in order tocompletely shut the light-emitting elements off the external side and toprevent, from the external side, the infiltration of substances such aswater and oxygen that deteriorate the organic compound layer upon theoxidation. It is therefore allowed to obtain a highly reliablelight-emitting device.

[0129] This Example can be put into practice in free combination withExample 1.

Example 3

[0130]FIG. 11 is a top view of the pixel unit of the light-emittingelement fabricated according to the method of Example 1. The circuitconstitution on the substrate is as shown in FIG. 11(A); i.e., there arearranged a drive circuit 1101 of the source side, a drive circuit 1102of the gate side and a pixel unit 1103.

[0131]FIG. 11(B) is a diagram illustrating, on an enlarged scale, aregion a (1104) of the pixel unit 1103 in which are formed pixelelectrodes (anodes in this Example) of the light-emitting elements andthe organic compound layer.

[0132] The source signal line 1105 is electrically connected to thedrive circuit 1101 of the source side. The current feeder line 1106 forsupplying the current to the light-emitting element is formed inparallel with the source signal line 1105.

[0133] Pixels 1107 formed in a plural number in the form of a matrix inthe pixel unit 1103 are each surrounded by the interlayer-insulatingfilm 1108.

[0134] After the organic compound layer has been formed, a cathode 1109which is an opposing electrode is formed as shown in FIG. 11(C). Here,however, the source signal line 1105 and the current feeder line 1106formed on the interlayer-insulating film 1108 are located at positionshigher than the surface of the substrate as compared to the pixels 1107and, hence, the cathode 1109 is cut off. That is, the cathode 1109 iscommon to the same sequence of pixels arranged in the longitudinaldirection facing the surface of the paper, but is not common to thesequence of pixels arranged in the transverse direction.

[0135] As shown in FIG. 11(C), therefore, the connection wiring 1110 isformed. The connection wiring 1110 has been formed alreadysimultaneously with the electrode wiring and the gate electrode. Uponelectrically connecting the cathode 1109 which serves as a wiring commonto plural pixels to the connection wiring 1110 on theinterlayer-insulating film 1108 through the connection portion shown inFIG. 11(C), therefore, all pixels are connected to the external powersource. The connection wiring 1110 may be formed at the lower portion ofthe pixel unit facing the surface of the paper as shown in FIG. 11(C) ormay be formed in the upper portion. Or, the connection wirings 1110 maybe formed at the upper and lower portions. These structures help preventlinear defect caused by the breakage of the cathode 1109 shared by thesequence of pixels. This Example can be put into practice in freecombination with the constitution of Example 1 or Example 2.

Example 4

[0136] An external light emitting quantum efficiency can be remarkablyimproved by using an organic material (which is also referred to astriplet compounds) by which phosphorescence from a triplet exciton canbe employed for emitting a light. As a result, the power consumption ofthe light-emitting element can be reduced, the lifetime of thelight-emitting element can be elongated and the weight of thelight-emitting element can be lightened.

[0137] The following is a report where the external light emittingquantum efficiency is improved by using the triplet exciton (T. Tsutsui,C. Adachi, S. Saito, Photochemical processes in Organized MolecularSystems, ed. K. Honda, (Elsevier Sci. Pub., Tokyo, 1991) p. 437).

[0138] The molecular formula of an organic material (coumarin pigment)reported by the above article is represented as follows.

[0139] (M. A. Baldo, D. F.O'Brien, Y. You, A. Shoustikov, S. Sibley, M.E. Thompson, S. R. Forrest, Nature 395 (1998) p.151)

[0140] The molecular formula of an organic material (Pt complex)reported by the above article is represented as follows.

[0141] (M. A. Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson, S. R.Forrest, Appl. Phys. Lett., 75 (1999) p.4.)

[0142] (T. Tsutsui, M. -J. Yang, M. Yahiro, K. Nakamura, T. Watanabe, T.Tsuji, Y. Fukuda, T. Wakimoto, S. Mayaguchi, Jpn, Appl. Phys., 38 (12B)(1999) L1502).

[0143] The molecular formula of an organic material (Ir complex)reported by the above article is represented as follows.

[0144] As described above, if phosphorescence from a triplet exciton canbe put to practical use, it can realize the external light emittingquantum efficiency three to four times as high as that in the case ofusing fluorescence from a singlet exciton in principle.

[0145] Further, it is possible that the organic material of thisembodiment is used to the organic compound layer of the light-emittingdevice shown in Embodiments 1 to 3.

Example 5

[0146] The light -emitting device fabricated in accordance with thepresent invention is of the self-emission type, and thus exhibits moreexcellent recognizability of the displayed image in a light place ascompared to the liquid crystal display device. Furthermore, thelight-emitting device has a wider viewing angle. Accordingly, variouselectronic devices can be completed by using the light-emitting deviceof the present invention to a display portion.

[0147] Such electronic devices include a video camera, a digital camera,a goggles-type display (head mount display), a navigation system, asound reproduction device (a car audio equipment and an audio set), alaptop personal computer, a game machine, a portable informationterminal (a mobile computer, a portable telephone, a portable gamemachine, an electronic book, or the like), an image reproductionapparatus including a recording medium (more specifically, an apparatuswhich can reproduce a recording medium such as a digital video disc(DVD) and so forth, and includes a display for displaying the reproducedimage), or the like. In particular, in the case of the portableinformation terminal, use of the self-emission device is preferable,since the portable information terminal that is likely to be viewed froma tilted direction is often required to have a wide viewing angle. FIG.12 respectively shows various specific examples of such electronicdevices.

[0148]FIG. 12A illustrates a display device which includes a frame 2001,a support table 2002, a display portion 2003, a speaker portion 2004, avideo input terminal 2005 or the like. The display device can becompleted by using the light-emitting device manufactured by the presentinvention to the display portion 2003. The light-emitting device is ofthe self-emission type and therefore requires no back light. Thus, thedisplay portion thereof can have a thickness thinner than that of theliquid crystal display device. The display device is including all ofthe display device for displaying information, such as a personalcomputer, a receiver of TV broadcasting and an advertising display.

[0149]FIG. 12B illustrated a digital still camera which includes a mainbody 2101, a display portion 2102, an image receiving portion 2103, anoperation key 2104, an external connection port 2105, a shutter 2106, orthe like. The digital still camera manufactured by the present inventioncan be completed by using the light-emitting device to the displayportion 2102.

[0150]FIG. 12C illustrates a laptop type personal computer whichincludes a main body 2201, a casing 2202, a display portion 2203, akeyboard 2204, an external connection port 2205, a pointing mouse 2206,or the like. The laptop type personal computer can be completed by usingthe light-emitting device manufactured by the present invention to thedisplay portion 2203.

[0151]FIG. 12D illustrated a mobile computer which includes a main body2301, a display portion 2302, a switch 2303, an operation key 2304,aninfrared port 2305, or the like. The mobile computer can be completed byusing the light-emitting device to the display portion 2302.

[0152]FIG. 12E illustrates an image reproduction apparatus including arecording medium (more specifically, a DVD reproduction apparatus),which includes a main body 2401, a casing 2402, a display portion A2403, another display portion B 2404, a recording medium (DVD or thelike) reading portion 2405, an operation key 2406, a speaker portion2407 or the like. The display portion A 2403 is used mainly fordisplaying image information, while the display portion B 2404 is usedmainly for displaying character information. The image reproductionapparatus can be completed by using the light-emitting devicemanufactured by the present invention to the display portion A 2403 andB 2404. The image reproduction apparatus including a recording mediumfurther includes a game machine or the like.

[0153]FIG. 12F illustrates a goggle type display (head mounted display)which includes a main body 2501, a display portion 2502, an arm portion2503. The light-emitting device in accordance with the present inventioncan be used as the display portion 2502.

[0154]FIG. 12G illustrates a video camera which includes a main body2601, a display portion 2602, an audio input portion 2603, an externalconnecting port 2604, a remote control receiving portion 2605, an imagereceiving portion 2606, a battery 2607, a sound input portion 2608, anoperation key 2609, or the like. The video camera can be completed byusing the light-emitting device manufactured by the present invention tothe display portion 2602.

[0155]FIG. 12H illustrates a mobile phone which includes a main body2701, a casing 2702, a display portion 2703, a sound input portion 2704,a sound output portion 2705, an operation key 2706, an externalconnecting port 2707, an antenna 2708, or the like. The mobile phone canbe completed by using the light-emitting device manufactured by thepresent invention to the display portion 2703. Note that the displayportion 2703 can reduce power consumption of the portable telephone bydisplaying white-colored characters on a black-colored background.

[0156] When the brighter luminance of the organic material becomesavailable in the future, the light-emitting device in accordance withthe present invention will be applicable to a front-type or rear-typeprojector in which light including output image information is enlargedby means of lenses or the like to be projected.

[0157] The aforementioned electronic devices are more likely to be usedfor display information distributed through a telecommunication pathsuch as Internet, a CATV (cable television system), and in particularlikely to display moving picture information. The light-emitting deviceis suitable for displaying moving pictures since the organic materialcan exhibit high response speed.

[0158] A portion of the light-emitting device that is emitting lightconsumes power, so it is desirable to display information in such amanner that the light-emitting portion therein becomes as small aspossible. Accordingly, when the light-emitting device is applied to adisplay portion which mainly displays character information, e.g., adisplay portion of a portable information terminal, and more particular,a portable telephone or a sound reproduction device, it is desirable todrive the light-emitting device so that the character information isformed by a light-emitting portion while a non-emission portioncorresponds to the background.

[0159] As set forth above, the light-emitting device formed by using thepresent invention can be applied variously to a wide range of electronicdevices in all fields. The electronic device in the present embodimentcan be completed by using a light-emitting device shown in Embodiments 1through 3 to the display portion.

[0160] According to this invention as described above, a function isimparted by utilizing the shape of the wiring to substitute for the bankthat has heretofore been formed by using a mask. Further, the shape ofthe wiring helps solve the problem of short-circuit between the wiringand the opposing electrode. The invention, therefore, makes it possibleto simplify the process for producing the light-emitting device and toproduce the devices maintaining a throughput higher than ever before.

1. A light-emitting device comprising: a TFT over a substrate; alight-emitting element over the substrate, the light-emitting elementcomprising a first electrode, an organic compound layer and a secondelectrode; a first wiring electrically connected to the first electrodeand provided over the substrate; an insulating film provided over thefirst wiring; and a second wiring formed over the first wiring and overthe insulating film, the second wiring electrically connected to theTFT.
 2. A device according to claim 1, wherein the light-emitting deviceis a display device.
 3. A device according to claim 1 wherein thelight-emitting device is incorporated into a digital still camera.
 4. Adevice according to claim 1 wherein the light-emitting device isincorporated into a notebook-type personal computer.
 5. A deviceaccording to claim 1 wherein the light-emitting device is incorporatedinto a mobile computer.
 6. A device according to claim 1 wherein thelight-emitting device is incorporated into a portable image-reproducingdevice equipped with a recording medium.
 7. A device according to claim1 wherein the light-emitting device is incorporated into a goggle-typedisplay.
 8. A device according to claim 1 wherein the light-emittingdevice is incorporated into a video camera.
 9. A device according toclaim 1 wherein the light-emitting device is incorporated into aportable telephone.
 10. A light-emitting device comprising: a TFT over asubstrate; a light-emitting element over the substrate, thelight-emitting element comprising a first electrode, an organic compoundlayer and a second electrode; a first wiring electrically connected tothe first electrode and provided over the substrate; an insulating filmprovided over the first wiring; a second wiring provided over the firstwiring and over the insulating film and electrically connected to theTFT; and a separation portion formed over the second wiring, theseparation portion comprising a material that provides an etching ratesmaller than that of a material forming the second wiring.
 11. A deviceaccording to claim 10, wherein the light-emitting device is a displaydevice.
 12. A device according to claim 10 wherein the light-emittingdevice is incorporated into a digital still camera.
 13. A deviceaccording to claim 10 wherein the light-emitting device is incorporatedinto a notebook-type personal computer.
 14. A device according to claim10 wherein the light-emitting device is incorporated into a mobilecomputer.
 15. A device according to claim 10 wherein the light-emittingdevice is incorporated into a portable image-reproducing device equippedwith a recording medium.
 16. A device according to claim 10 wherein thelight-emitting device is incorporated into a goggle-type display.
 17. Adevice according to claim 10 wherein the light-emitting device isincorporated into a video camera.
 18. A device according to claim 10wherein the light-emitting device is incorporated into a portabletelephone.
 19. A light-emitting device comprising: a TFT over asubstrate; a light-emitting element over the substrate, thelight-emitting element comprising a first electrode, an organic compoundlayer and a second electrode; a first wiring electrically connected tothe first electrode and provided over the substrate; an insulating filmprovided over the first wiring; a second wiring provided over the firstwiring and over the insulating film and electrically connected to theTFT; and a separation portion provided over the second wiring, theseparation portion serving as a mask in forming the organic compoundlayer and the second electrode.
 20. A device according to claim 19,wherein the light-emitting device is a display device.
 21. A deviceaccording to claim 19 wherein the light-emitting device is incorporatedinto a digital still camera.
 22. A device according to claim 19 whereinthe light-emitting device is incorporated into a notebook-type personalcomputer.
 23. A device according to claim 19 wherein the light-emittingdevice is incorporated into a mobile computer.
 24. A device according toclaim 19 wherein the light-emitting device is incorporated into aportable image-reproducing device equipped with a recording medium. 25.A device according to claim 19 wherein the light-emitting device isincorporated into a goggle-type display.
 26. A device according to claim19 wherein the light-emitting device is incorporated into a videocamera.
 27. A device according to claim 19 wherein the light-emittingdevice is incorporated into a portable telephone.
 28. A light-emittingdevice comprising: a TFT over a substrate; a light-emitting element overthe substrate, the light-emitting element having a first electrode, anorganic compound layer and a second electrode; a first wiring providedover the substrate; an insulating film provided over the first wiring,and a second wiring provided over the first wiring and over theinsulating film and electrically connected to the TFT; wherein the firstelectrode is provided in contact with the first wiring only.
 29. Adevice according to claim 28, wherein the light-emitting device is adisplay device.
 30. A device according to claim 28 wherein thelight-emitting device is incorporated into a digital still camera.
 31. Adevice according to claim 28 wherein the light-emitting device isincorporated into a notebook-type personal computer.
 32. A deviceaccording to claim 28 wherein the light-emitting device is incorporatedinto a mobile computer.
 33. A device according to claim 28 wherein thelight -emitting device is incorporated into a portable image-reproducingdevice equipped with a recording medium.
 34. A device according to claim28 wherein the light-emitting device is incorporated into a goggle-typedisplay.
 35. A device according to claim 28 wherein the light-emittingdevice is incorporated into a video camera.
 36. A device according toclaim 28 wherein the light-emitting device is incorporated into aportable telephone.
 37. A light-emitting device comprising: pluralpixels provided over a substrate and arranged in an active matrix; adrive circuit provided over said substrate; and a light-emitting elementprovided in each of said plural pixels and comprising a first electrode,an organic compound layer and a second electrode, wherein the secondelectrode comprises a film on a same plane for each sequence of pixelsprovided along a wiring that is electrically connected to the drivecircuit.
 38. A device according to claim 37, wherein the light-emittingdevice is a display device.
 39. A device according to claim 37 whereinthe light-emitting device is incorporated into a digital still camera.40. A device according to claim 37 wherein the light-emitting device isincorporated into a notebook-type personal computer.
 41. A deviceaccording to claim 37 wherein the light-emitting device is incorporatedinto a mobile computer.
 42. A device according to claim 37 wherein thelight-emitting device is incorporated into a portable image-reproducingdevice equipped with a recording medium.
 43. A device according to claim37 wherein the light-emitting device is incorporated into a goggle-typedisplay.
 44. A device according to claim 37 wherein the light-emittingdevice is incorporated into a video camera.
 45. A device according toclaim 37 wherein the light-emitting device is incorporated into aportable telephone.
 46. A method of fabricating a light-emitting devicecomprising: forming source, drain and channel regions over a substrate;forming a gate-insulating film to cover the source, drain and channelregions; forming a gate electrode and a first wiring; forming aninsulating film over the gate electrode and over the first wiring;removing part of the insulating film formed over the first wiring;forming a second wiring over the first wiring and over the insulatingfilm, the second wiring electrically connected to one of the source andthe drain; forming a separation portion over the second wiring; andforming a light-emitting element electrically connected to the firstwiring.
 47. A method according to claim 46, wherein the light-emittingdevice is a display device.
 48. A method according to claim 46 whereinthe light-emitting device is incorporated into a digital still camera.49. A method according to claim 46 wherein the light-emitting device isincorporated into a notebook-type personal computer.
 50. A methodaccording to claim 46 wherein the light-emitting device is incorporatedinto a mobile computer.
 51. A method according to claim 46 wherein thelight-emitting device is incorporated into a portable image-reproducingdevice equipped with a recording medium.
 52. A method according to claim46 wherein the light-emitting device is incorporated into a goggle-typedisplay.
 53. A method according to claim 46 wherein the light-emittingdevice is incorporated into a video camera.
 54. A method according toclaim 46 wherein the light-emitting device is incorporated into aportable telephone.
 55. A method of fabricating a light-emitting devicecomprising: forming source, drain and channel regions over a substrate;forming a gate-insulating film to cover the source, drain and channelregions; forming a gate electrode and a first wiring; forming aninsulating film over the gate electrode and over the first wiring;removing part of the insulating film formed over the first wiring;forming a second wiring over the first wiring and over the insulatingfilm, the second wiring electrically connected to one of the source andthe drain; forming a separation portion over the second wiring; andforming a first electrode, an organic compound layer and a secondelectrode of a light-emitting element by using the separation portion asa mask.
 56. A method according to claim 55, wherein the light-emittingdevice is a display device.
 57. A method according to claim 55 whereinthe light-emitting device is incorporated into a digital still camera.58. A method according to claim 55 wherein the light-emitting device isincorporated into a notebook-type personal computer.
 59. A methodaccording to claim 55 wherein the light-emitting device is incorporatedinto a mobile computer.
 60. A method according to claim 56 wherein thelight-emitting device is incorporated into a portable image-reproducingdevice equipped with a recording medium.
 61. A method according to claim57 wherein the light-emitting device is incorporated into a goggle-typedisplay.
 62. A method according to claim 58 wherein the light-emittingdevice is incorporated into a video camera.
 63. A method according toclaim 59 wherein the light-emitting device is incorporated into aportable telephone.
 64. A method of fabricating a light-emitting devicecomprising: forming source, drain and channel regions over a substrate;forming a gate-insulating film to cover the source, drain and channelregions; forming a gate electrode and a first wiring; forming a firstinsulating film over the gate electrode and over the first wiring;removing part of the first insulating film formed over the first wiring;forming a second wiring over the first wiring and over the firstinsulating film, the second wiring electrically connected to one of thesource and the drain; forming a second insulating film over the secondwiring; and forming a partitioning wall by etching the second wiring andthe second insulating film by a wet-etching method.
 65. A methodaccording to claim 64, wherein the light-emitting device is a displaydevice.
 66. A method according to claim 64 wherein the light-emittingdevice is incorporated into a digital still camera.
 67. A methodaccording to claim 64 wherein the light-emitting device is incorporatedinto a notebook-type personal computer.
 68. A method according to claim64 wherein the light-emitting device is incorporated into a mobilecomputer.
 69. A method according to claim 64 wherein the light-emittingdevice is incorporated into a portable image-reproducing device equippedwith a recording medium.
 70. A method according to claim 64 wherein thelight-emitting device is incorporated into a goggle-type display.
 71. Amethod according to claim 64 wherein the light-emitting device isincorporated into a video camera.
 72. A method according to claim 64wherein the light-emitting device is incorporated into a portabletelephone.
 73. A method of fabricating a light-emitting devicecomprising: forming source, drain and channel regions over a substrate;forming a gate-insulating film to cover the source, drain and channelregions; forming a gate electrode and a first wiring; forming aninsulating film over the gate electrode and over the first wiring;removing part of the insulating film formed over the first wiring;forming a second wiring over the first wiring and over the insulatingfilm, the second wiring electrically connected to one of the source andthe drain; forming a separation portion over the second wiring; andforming a first electrode, an organic compound layer and a secondelectrode of a light-emitting element by using the separation portion asa mask, wherein the first wiring is formed in contact with the firstelectrode.
 74. A method according to claim 73, wherein thelight-emitting device is a display device.
 75. A method according toclaim 73 wherein the light-emitting device is incorporated into adigital still camera.
 76. A method according to claim 73 wherein thelight-emitting device is incorporated into a notebook-type personalcomputer.
 77. A method according to claim 73 wherein the light-emittingdevice is incorporated into a mobile computer.
 78. A method according toclaim 73 wherein the light-emitting device is incorporated into aportable image-reproducing device equipped with a recording medium. 79.A method according to claim 73 wherein the light-emitting device isincorporated into a goggle-type display.
 80. A method according to claim73 wherein the light-emitting device is incorporated into a videocamera.
 81. A method according to claim 73 wherein the light-emittingdevice is incorporated into a portable telephone.